SteveJ

Well, it looks like you don't have a short to ground between the fuel light and the sending unit, otherwise you would have gotten the fuel light with the sending unit unplugged. You seem to have good resistance at the thermistor (1kOhm between the yellow/blue and black wires). You could pull the sending unit and see if the thermistor was covered with gas. It seems like it is not immersed in fuel with the meter readings you got.

Oh and you might turn the key to ON with the sending unit disconnected. If you get the low fuel light in that case, you have a cross connection.

So now measure resistance from the yellow/blue to the black on the wiring harness side of the connector. After we rule out a short In the wiring harness, you'll take some voltage readings.

It could be resistance in the connectors or in the turn signal switch dropping the voltage.

Disconnect the fuel sending unit. Check resistance on both sides of the connector from yellow/blue to black. (Note: the wire color could be different on the sending unit. Check the pin that goes to the yellow/blue wire in the body harness.) Report your results here.

Variable speed flasher: https://www.amazon.com/gp/product/B011BTMDQM Low speed is due to low voltage. The voltage could be low due to corrosion at all of the connectors. Is the turn signal faster when driving than when idling at a light?

No buzzer for the passenger door. The wiring is different between the two switches. There is an extra wire on the driver side door switch for the key-in buzzer.

The switch body/wiring is the same 70-73.

I think I'll be doing that soon for Bill's car, @David Downs. I have the carbs tuned nice, but it is starving for fuel.

I think @Dave WM was using two bulbs because they were 6 volt bulbs.

There are different part numbers for the hazard flasher and turn signal flasher in the parts manual. The hazard flasher part number is still available in the Nissan system, but the turn signal part numbers are NLA. Of course, when I swapped out all of the lights to LED, I went with electronic flashers that for all intents and purposes are interchangeable...but I digress.

That's the problem when you license and replicate someone else's design. You usually copy the design flaws, too. You won't find connectors/narrow pins like the 75-77 EFI relay connectors anywhere else in the Z. Those came the Bosch design. Of course, if my designs were perfect, I wouldn't need another engineer to review them...and there would never be red-lines on the drawings from the production floor/startup. Heck, I just carry a red pen with me at work to save time. I never have to hunt for one.

Does the serial number correspond to the information on the website description?

Can you figure out the wattage of those two bulbs? It may help someone else who buys the ZCD sending unit.

By the way, Rockauto does have a replacement for the transistor ignition unit. Just look for ICM when you drill down on their site. I cannot vouch for the quality of any of the parts listed. Many people have gone with the HEI because it is relatively economical.

The original 280Z EFI system was licensed from Bosch. If you look at the link I posted, you'll see that Nissan used many of the same terminal numbers, such as 36 & 39 for the AFM flap. Why re-create relays on a licensed system? Over at ZCar.com many years ago, there were threads about using the VW EFI relays to replace the NLA Nissan EFI relays. The "two Bosch relays to replace the Nissan NLA relay" is for the ignition relay. ZCarDepot sells it now. They can beat me on cost, so they can have the business. I can be pretty sure my answer is correct because @Captain Obvious basically posted the same idea about the connectors. I just put some terminal numbers on mine to line up with the wiring diagram a little better.

It could be the TIU in the passenger footwell. @EuroDat contributed this to the collective knowledge:

Well, it took less time than I thought. Line up your connectors this way. From the wiring diagram

Is it a stock distributor/ignition? If you're not sure, you'll need to post pictures or look at the EE section of the factory service manual (found in the Resources/downloads section of this site).

I'll just leave this link here for now. I'll look at it more tomorrow and add to the discussion about the pins on the relays. There is some good information here: https://www.ratwell.com/technical/DoubleRelay.html

What brand pump? There seems to be some issues with mechanical fuel pumps over the last year or so.

Thank you for posting the photo of the EFI fusible link. Did you check to see if you had 12 VDC at pin 70 of the EFI relay? If you do, then I would focus on the ECU and why it's not providing the ground at the EFI relay.

Just to clarify. Do you still have the mechanical pump at the engine?

Also, where did you mount the electric fuel pump, and what is the orientation? What does the manufacturer's installation instructions say? What brand/model electric pump did you install?

Make sure your fuel filter (stock design) is mounted vertically with the outlet on top. Inside the fuel filter, the opening for the outlet is low when the filter is mounted properly, so the fuel does not fill the filter typically. I hope this image give you a good visual. The photos you posted are in a format that users with Windows computers cannot open easily. I am lazy and do not care to install software that allows me to look at them. You may want to look at converting the photos to a JPG format. As for fuel starving, go back and give us details. Why did you add in the electric fuel pump? Do all of the fuel lines have smooth bends that don't kink the hoses? Have you checked the fuel pressure between the pumps? You don't want too much pressure (>4 PSI) on the fuel rail, as you will overwhelm the floats.